A typical loading dock includes one or more dock openings or doorways each enclosed by an overhead door. In many cases, a dock leveler is mounted in a pit in the loading dock in front of the doorway and operation of the dock leveler will serve to bridge the gap between the loading dock and a truck parked in front of the dock so that personnel and material handling equipment, such as a forklift truck, can conveniently move between the loading dock and the truck bed.
During a loading operation the truck body will enclose the doorway in the dock, but when a loading dock operation is not taking place, it is often desired to maintain the overhead door in an open position to provide increased ventilation or light in the building or to vent smoke, fumes or odors from the building. With the overhead door in the open position, there is a problem of unauthorized personnel entering the building as well as articles being passed through the opening by pilferage.
Another problem that arises when the overhead door is open is that there is a possibility that material equipment, such as a forklift truck, maneuvering on the dock may accidentally back through the open doorway and fall to the driveway, thus causing possible injury to personnel or damage to the equipment.